A new analysis of the surface of Venus shows signs of tectonic movement in the form of crustal blocks that have jostled against each other like shattered pieces of ice floe. The movement of these blocks could indicate that Venus is still geologically active, and give scientists insight into both exoplanet tectonics and early tectonic activity on Earth.
“We have identified a hitherto unrecognized tectonic deformation pattern on Venus, which is driven by inner movement just as it is on Earth,” said Paul Byrne, associate professor of planetary science at Carolina State University. North and main author and co-correspondent of the work. “Although different from the tectonics we are currently seeing on Earth, it is still evidence of an inner movement expressed on the surface of the planet.”
The discovery is significant because Venus has long been believed to have an immobile solid outer shell, or lithosphere, much like Mars or Earth’s Moon. In contrast, the Earth’s lithosphere is divided into tectonic plates, which slide against each other, apart and under each other, above a warm, weaker mantle layer.
Byrne and an international group of researchers used radar images from NASA’s Magellan mission to map the surface of Venus. Examining the vast Venusian plains that make up most of the planet’s surface, they saw areas where large boulders of the lithosphere appear to have moved: separate, come closer, spin, and slide over each other. like broken ice on a frozen lake.
The team created a computer model of this deformation and found that the slow motion of the planet’s interior may explain the style of tectonics seen on the surface.
“These observations tell us that inner movement causes the surface to deform on Venus, in a similar way to what happens on Earth,” Byrne explains. “Plate tectonics on Earth are driven by convection in the mantle. The mantle is hot or cold in different places, it moves, and part of this motion is transferred to the Earth’s surface in the form of motion plates.
“A variation on this theme also seems to play out on Venus. It is not plate tectonics like on Earth – there are no huge mountain ranges created here, nor giant subduction systems – but it is ‘is evidence of deformation due to internal mantle flow, which has never been demonstrated on a global scale before. ”
The deformation associated with these crustal blocks could also indicate that Venus is still geologically active.
“We know that a large part of Venus has resurfaced volcanically over time, so parts of the planet could be very young, geologically speaking,” Byrne explains. “But several of the jostling boulders formed and deformed these young lava plains, which means that the lithosphere fragmented after the establishment of these plains. This gives us reason to believe that some of these boulders may have moved geologically very recently – perhaps even until today. “
Researchers are optimistic that the newly recognized “ice floe” model of Venus may offer clues to understanding tectonic deformation on planets outside of our solar system, as well as on a much younger Earth.
“The thickness of a planet’s lithosphere depends primarily on its temperature, both inside and on the surface,” Byrne explains. “The heat flux from within young Earth was up to three times greater than it is now, so its lithosphere may have been similar to what we see on Venus today: no thick enough to form plates that subduct, but thick enough to have fragmented into blocks that pushed, pulled, and jostled each other. “
NASA and the European Space Agency recently approved three new space missions to Venus that will acquire observations of the planet’s surface at a much higher resolution than Magellan. “It’s great to see a renewed interest in exploring Venus, and I’m especially excited that these missions can test our key finding that the planet’s lowlands have fragmented into jostling crustal blocks.” , Byrne said.